Control panel system



Oct. 31, 1961 w. c. SEALEY 3,007,108

CONTROL PANEL SYSTEM Filed Nov. 4, 1957 49 M KW United States PatentOfifice 3,ll7,l%8 Patented Oct. 31, 1961 3,007,108 CONTROL PANEL SYSTEMWilliam C. fiealey, Wauwatosa, Wis., assignor to Allis- ChalmersManufacturing Company, Milwaukee, Wis. Filed Nov. 4, 1957, Ser. No.6%,238 4 Claims. (Cl. 324-28) This invention relates in general to acontrol panel for electrical regulating apparatus and more specificallyto a novel means for providing an adjustable voltage for calibrating ortesting the voltage sensing means of a voltage or phase angle regulator.

Voltage sensing means are frequently used for automatically controllingthe switching of capacitors or transformer taps to regulate the phaseangle or voltage of an electrical distribution network. The voltagesensing device and the circuit elements linking it with the motorcontrols of the regulator are generally referred to as the controlpanel. Magnetic relays which are actuated by the voltage of theregulated system are often used for this voltage sensing purpose. Relaysgenerally have electrical or mechanical adjustments for determining thepoints at which the relay contacts close and for determining the bandwidth or voltage range over which the contacts remain open. When theregulator is installed in the field, the relay is set to the desiredvoltage level and band width. A calibrating or testing voltage of thedesired range is applied to the relay circuit and the electrical ormechanical adjustments are made until the desired relay action isobtained. Since the relay actuating voltage from the transmission linemay be below the voltage required for the maximum test voltage it isnecessary to provide some means for increasing this voltage. Inasmuch asthe relay may be checked or reset periodically throughout its years ofservice it is desirable to include the voltage raising means as a partof the control panel.

One simple way of raising the voltage to the relay is to operate theregulator manually to raise the line voltage. However, this temporarilydefeats the purpose of the regulator as it changes the voltage suppliedto the load.

Another method of the prior art for obtaining the desired test voltagecalls for a variable autotransforrner which is connected into the panelduring the test. This method of obtaining a higher voltage isunsatisfactory because of the difficulty in isolating the panel andmaking the connections to the autotransformer. Providing a permanentlyconnected auto transfo-rmer is also unsatisfactory because theautotransformer is expensive and requires appreciable space in thecontrol panel cabinet.

This invention provides a simple means for raising the voltage acrossthe voltage sensitive relay to the desired level for a test orcalibration by calling for a capacitor and variable resistance which canbe connected in series with the relay. It is well known that the totalimpedance of a circuit containing an inductance such as a magnetic relaymay be lowered by introducing a capacitance in the circuit. The voltageacross the inductance and the other circuit elements will be raised bythe increased current. The voltage may then be adjusted to the levelrequired for the test by means of the variable resistance. The voltageraising device of this invention is simple and inexpensive tomanufacture and it provides a wide range of voltage values both aboveand below the available signal voltage.

Therefore, it is an object of this invention to provide a new andimproved control panel for a regulating device.

Another object of this invention is to provide a new and improved meansfor adjusting the signal to a voltage sensitive control device to alevel above or below the existing signal.

responds by signaling the regulator.

Objects and advantages will be apparent from the following descriptionwhen read in connection with the accompanying drawings in which:

FIG. 1 is an impedance diagram illustrating the effects of reducing thetotal reactance in a circuit;

FIG. 2 is a schematic view of a regulator control panel; and

FIG. 3 is a vector diagram illustrating the voltage raising andadjusting effect of the control panel using this invention.

While numerous control circuits exist to which this invention isapplicable, it may conveniently be illustrated in connection with aconventional voltage regulator control panel using a line dropcompensator.

Referring to the drawing and particularly to FIG. 1 the total impedanceof an electrical circuit may be varied by changing the total reactanceof the circuit. Thus, a circuit containing a resistance R in series withan inductance X and no capacitance has a total impedance Z Byintroducing into the circuit a capacitance X which counteracts in partinductance X the total impedance of the circuit is reduced to a value ZIt is apparent that where the current of a circuit having a constantvoltage input equals the voltage divided by the total impedance thecurrent Will increase upon a decrease in the impedance.

It is this principle of increasing the line current by decreasing totalimpedance which is embodied in applicants novel device for testing orcalibrating a reactance circuit such as a voltage regulating device in acontrol panel of a regulator. The control panel 11 of FIG. 2 cooperateswith a conventional tap changer and motor, not shown for simplicity, toregulate the voltage in a power line. Panel 11 comprises a potentialcircuit 12 and a current circuit 13. The potential circuit comprises apotential transformer 14, a voltage sensitive regulating relay 16, afirst variable resistor 17, a variable inductance 18 and a secondvariable resistance 19. The current circuit includes a currenttransformer ll and is coupled to the potential circuit by variableinductance 18 and variable resistance 19. The combination of the currentcircuit and inductance 18 and resistance 19 is generally referred to inthe trade as a line drop compensator. Its purpose is for raising theoutput voltage sufiiciently to compensate for the voltage drop from theregulator to the load center.

In operation potential transformer 14 which is connected across theoutput terminals of the regulator supplies a proportionately reducedvoltage to voltage regulating relay 16. The voltage across relay 16 isthe combination of the voltage at the regulator as measured by potentialtransformer 14 and the voltage drop in a portion of the transmissionline as measured by current transformer 21 in combination with variableinductance 18 and variable resistance 19. Relay 16 is responsive tovoltage variations with respect to a predetermined voltage band width.The desired range of voltages at which relay 16 is balanced is obtainedby adjusting variable resistance 17. Thus, when the output voltage dropsbelow its desired level the relay becomes unbalanced and The regulatorautomatically raises its output voltage to compensate for the drop andcontinues to do so until relay 16 is again balanced. Relay 16 and theregulator cooperate in a similar manner when the output voltage of theregulator is too high.

It is generally desirable to occasionally test the accuracy of relay 16in responding to the predetermined voltage range. This inventionprovides a means for providing a test voltage or meter voltage V asreferred to in FIG. 3, which simulates voltages normally obtained frompotential transformer 14, thus eliminating the need for altering theoutput voltage of the regulator and potential transformer 14 which wouldadversely affect the operation of the regulator. In normal operation amovable contact 22 rests on contact 23. Inasmuch as the compensator isnot needed in testing the relay it is switched out by moving contact 27from contact 28 to contact 29, thus short circuiting current transformer21. In order to test relay 16, contact 22 is moved over to contact 24,causing the insertion of a series connected capacitance 26. The movingof contacts 22 and 27 may be simplified by mechanically linking them,enabling one to move both contacts simultaneously. Such mechanicallinkage is preferable also as a protective measure for if the currenttransformer is not short circuited an undesirable high voltage may occuracross the current transformer primary winding.

A voltmeter 31 is connected in parallel with the impressed voltage andthe series connected load and indicates the voltage of the potentialcircuit 11 which influences relay 16. Prior to the insertion ofcapacitance 26 voltmeter 31 reads the impressed voltage V; oftransformer 14- or the vectorial addition of I R and I X vectoriallyshown in FIG. 3. As illustrated, the current I of the circuit whencapacitance 26 is electrically isolated from the circuit lags voltage V;at an angle a. This is a result of the lagging effect of the inductanceobtained from variable inductance 18 and the coil of relay 16. However,upon adding capacitance 26, the new current, now referred to as I in thepotential circuit lags the voltage V at a smaller angle b. As mentionedpreviously and illustrated in FIG. 1, insertion of capacitance 26reduces the total impedance of the circuit and, consequent- 1y, I isgreater than 1 Therefore, the new resistive component 1 R and newinductance component I X are both greater than their original values.With capacitance 26 inserted in the circuit, voltmeter 31 no longerreads the impressed voltage of transformer 14, but now reads thevectorial addition of 1 R and I X The test or meter voltage V which isnow affecting relay 16 and is read on the voltmeter is of a larger valuethan V the original impressed voltage aifecting relay 16. V may also beread as the vectorial addition of V; and I X Means must also be providedfor obtaining a voltage reading less than V; in order to test theeffectiveness of relay 16 in reacting to a subnormal voltage. This isaccomplished by connecting variable resistance 32, preferably arheostat, in series with capacitance 26 and relay 16. Movable contact 22is adjusted on resistance 32 until the voltmeter reads the desiredvalue. The insertion of more resistance into the circuit causes theresistive component 1 R of FIG. 3 to become smaller since I is nowsmaller. Consequently, V is also reduced in magnitude.

Upon completion of the relay test movable contacts 22 and 27 arereturned to stationary contacts 23 and 28, respectively, and,consequently, voltage sensitive relay 16 is restored to its normaloperating condition. Unlike tests of the prior art there is no need forresetting and adjusting variable inductance 18 and variable resistance19. Nor has the output voltage of the regulator been altered at any timeduring the test or calibration of the relay.

While but only one embodiment of this invention has been described itwill be obvious to those skilled in the art that modifications can bemade within the scope of the appended claims and that a relay is merelyillustrative-0 f other reactive voltage sensing devices such as contactmaking motors and magnetic amplifiers used in various types ofregulating systems.

What is claimed is:

1. In an electrical regulating apparatus: a linear reactance circuithaving a voltage sensitive device, a reactance of opposite phasedisplacement from said linear reactance circuit, a variable resistorconnected to said opposite phase reactance, and a switching means forselectively switching said variable resistor and reactance in and out ofsaid reactance circuit for raising the voltage across said circuit to afirst value and lowering the voltage across said circuit to a secondvalue to test the response of said voltage sensitive device to voltagesbetween said first and second values.

2. In an electrical regulating apparatus: a linear reactance circuithaving a voltage sensitive device responsive to a signal of a varyingvoltage, a reactance of opposite phase displacement from the linearreactance of said circuit, means for inserting said opposite phasereactance into said linear reactance circuit whereby the voltage acrosssaid circuit is raised to a value substantially equal to the highestexpected signal voltage, and a variable resistor connected with saidreactance to vary the voltage across said linear reactance circuit to avalue substantially equal to the lowest expected signal voltage to testthe response of said voltage sensitive device.

3. In an electrical regulating apparatus a reactance circuit having avoltage sensitive device responsive to a signal of a varying voltage, areactance of opposite phase displacement from the reactance of saidcircuit having one end connected to said circuit, the other end of saidopposite phase reactance connected to a variable resistor, and a singlemeans for selectively inserting said reactance and variable portions ofsaid resistor to said linear reactance circuit whereby the voltageacross said circuit may vary from a value substantially equal to thehighest expected signal voltage to a value substantially equal to thelowest expected signal voltage.

4. In a voltage regulating apparatus: a linear inductive circuit havinga voltage sensitive device connected across a source of a signal of avarying voltage, a capacitor connected at one end to said linearinductive circuit, the other end of said capacitor connected to avariable resistor, a movable contact connected to said circuit forswitching said capacitor in series with said circuit to raise thevoltage across said voltage responsive device to a value substantiallyequal to the highest expected signal voltage, said movable contactfurther operable across the full range of said variable resistor to varythe voltage across said device to a value substantially equal to thelowest expected signal voltage to test the response of said device.

References Cited in the file of this patent UNITED STATES PATENTS2,668,942 Varela Feb. 9, 1954 2,906,942 Mittag Sept. 29, 1959 FOREIGNPATENTS 110,785 Australia Oct. 10, 1928 431,422 Great Britain July 8,1935

